Issue when building Ipopt-3.12.x

[Vuong Le]

Hi @baumanab , @domluna ,

In your Readme give an instruction for install Ipopt:

• You just need to download the source from the Ipopt releases page or the Github releases page.

And I saw that the Ipopt releases page or the Github releases page have a little different.

• Ipopt releases page: build with script install_ipopt.sh success

• Github releases: build error because it lack ThirdParty and BuildTools folder

Maybe someone will have this issue and take a lot of time to correct it.
So if possible, please consider to update this information into your instruction.

[Siu Wa Wu]

+1. I also encounter the same issue while I am install Ipopt-3.12.1.
The Github release failed, and Ipopt release page succeed.

[Dominique Luna]

Hey guys, I thought I deleted the Github release page already, guess I didn't! Anyway I removed the link to it, not sure why the zip files are different.